--- /dev/null
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Alwin Antreich <a.antreich@proxmox.com>
+Date: Thu, 6 Dec 2018 12:14:04 +0100
+Subject: [PATCH] os/bluestore: handle spurious read errors
+
+Some kernels (4.9+) sometime fail to return data when reading
+from a block device under memory pressure. This patch retries
+the read if the checksum verification fails, tests show that
+the first retried read succeeds in ~99.5% of the cases, so
+3 attempts are made by default before giving up on the data.
+
+Works-around: http://tracker.ceph.com/issues/22464
+Signed-off-by: Paul Emmerich <paul.emmerich@croit.io>
+(cherry picked from commit cffcbc73aaaa874829d5fc9091af3042b887f9a7)
+
+ Conflicts:
+ src/common/legacy_config_opts.h
+- adjacent options
+ src/common/options.cc
+- no RUNTIME flag in luminous
+ src/os/bluestore/BlueStore.cc
+ src/os/bluestore/BlueStore.h
+- adjacent perfcounter
+ src/test/objectstore/store_test.cc
+- adjacent tests, no #ifdef
+- g_conf, not g_conf()
+- no create_new_collection
+- queue_transaction etc take osr, not ch
+
+Signed-off-by: Alwin Antreich <a.antreich@proxmox.com>
+---
+ src/common/legacy_config_opts.h | 2 +
+ src/common/options.cc | 10 +++++
+ src/os/bluestore/BlueStore.cc | 35 ++++++++++++++--
+ src/os/bluestore/BlueStore.h | 4 +-
+ src/test/objectstore/store_test.cc | 67 ++++++++++++++++++++++++++++++
+ 5 files changed, 114 insertions(+), 4 deletions(-)
+
+diff --git a/src/common/legacy_config_opts.h b/src/common/legacy_config_opts.h
+index a51870ef6..54d2b578b 100644
+--- a/src/common/legacy_config_opts.h
++++ b/src/common/legacy_config_opts.h
+@@ -1031,6 +1031,7 @@ OPTION(bluestore_block_preallocate_file, OPT_BOOL) //whether preallocate space i
+ OPTION(bluestore_csum_type, OPT_STR) // none|xxhash32|xxhash64|crc32c|crc32c_16|crc32c_8
+ OPTION(bluestore_csum_min_block, OPT_U32)
+ OPTION(bluestore_csum_max_block, OPT_U32)
++OPTION(bluestore_retry_disk_reads, OPT_U64)
+ OPTION(bluestore_min_alloc_size, OPT_U32)
+ OPTION(bluestore_min_alloc_size_hdd, OPT_U32)
+ OPTION(bluestore_min_alloc_size_ssd, OPT_U32)
+@@ -1124,6 +1125,7 @@ OPTION(bluestore_debug_omit_kv_commit, OPT_BOOL)
+ OPTION(bluestore_debug_permit_any_bdev_label, OPT_BOOL)
+ OPTION(bluestore_shard_finishers, OPT_BOOL)
+ OPTION(bluestore_debug_random_read_err, OPT_DOUBLE)
++OPTION(bluestore_debug_inject_csum_err_probability, OPT_FLOAT)
+
+ OPTION(kstore_max_ops, OPT_U64)
+ OPTION(kstore_max_bytes, OPT_U64)
+diff --git a/src/common/options.cc b/src/common/options.cc
+index ff3bb1a1b..8983210d9 100644
+--- a/src/common/options.cc
++++ b/src/common/options.cc
+@@ -3422,6 +3422,12 @@ std::vector<Option> get_global_options() {
+ .set_description("Maximum block size to checksum")
+ .add_see_also("bluestore_csum_min_block"),
+
++ Option("bluestore_retry_disk_reads", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
++ .set_default(3)
++ .set_min_max(0, 255)
++ .set_description("Number of read retries on checksum validation error")
++ .set_long_description("Retries to read data from the disk this many times when checksum validation fails to handle spurious read errors gracefully."),
++
+ Option("bluestore_min_alloc_size", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
+ .set_default(0)
+ .add_tag("mkfs")
+@@ -3791,6 +3797,10 @@ std::vector<Option> get_global_options() {
+ .set_default(0)
+ .set_description(""),
+
++ Option("bluestore_debug_inject_csum_err_probability", Option::TYPE_FLOAT, Option::LEVEL_DEV)
++ .set_default(0.0)
++ .set_description("inject crc verification errors into bluestore device reads"),
++
+ // -----------------------------------------
+ // kstore
+
+diff --git a/src/os/bluestore/BlueStore.cc b/src/os/bluestore/BlueStore.cc
+index b326d39bc..28ababbe5 100644
+--- a/src/os/bluestore/BlueStore.cc
++++ b/src/os/bluestore/BlueStore.cc
+@@ -4171,6 +4171,8 @@ void BlueStore::_init_logger()
+ "collection");
+ b.add_u64_counter(l_bluestore_read_eio, "bluestore_read_eio",
+ "Read EIO errors propagated to high level callers");
++ b.add_u64_counter(l_bluestore_reads_with_retries, "bluestore_reads_with_retries",
++ "Read operations that required at least one retry due to failed checksum validation");
+ logger = b.create_perf_counters();
+ cct->get_perfcounters_collection()->add(logger);
+ }
+@@ -6698,7 +6700,8 @@ int BlueStore::_do_read(
+ uint64_t offset,
+ size_t length,
+ bufferlist& bl,
+- uint32_t op_flags)
++ uint32_t op_flags,
++ uint64_t retry_count)
+ {
+ FUNCTRACE();
+ int r = 0;
+@@ -6919,7 +6922,14 @@ int BlueStore::_do_read(
+ bufferlist& compressed_bl = *p++;
+ if (_verify_csum(o, &bptr->get_blob(), 0, compressed_bl,
+ b2r_it->second.front().logical_offset) < 0) {
+- return -EIO;
++ // Handles spurious read errors caused by a kernel bug.
++ // We sometimes get all-zero pages as a result of the read under
++ // high memory pressure. Retrying the failing read succeeds in most cases.
++ // See also: http://tracker.ceph.com/issues/22464
++ if (retry_count >= cct->_conf->bluestore_retry_disk_reads) {
++ return -EIO;
++ }
++ return _do_read(c, o, offset, length, bl, op_flags, retry_count + 1);
+ }
+ bufferlist raw_bl;
+ r = _decompress(compressed_bl, &raw_bl);
+@@ -6937,7 +6947,14 @@ int BlueStore::_do_read(
+ for (auto& reg : b2r_it->second) {
+ if (_verify_csum(o, &bptr->get_blob(), reg.r_off, reg.bl,
+ reg.logical_offset) < 0) {
+- return -EIO;
++ // Handles spurious read errors caused by a kernel bug.
++ // We sometimes get all-zero pages as a result of the read under
++ // high memory pressure. Retrying the failing read succeeds in most cases.
++ // See also: http://tracker.ceph.com/issues/22464
++ if (retry_count >= cct->_conf->bluestore_retry_disk_reads) {
++ return -EIO;
++ }
++ return _do_read(c, o, offset, length, bl, op_flags, retry_count + 1);
+ }
+ if (buffered) {
+ bptr->shared_blob->bc.did_read(bptr->shared_blob->get_cache(),
+@@ -6981,6 +6998,11 @@ int BlueStore::_do_read(
+ assert(pos == length);
+ assert(pr == pr_end);
+ r = bl.length();
++ if (retry_count) {
++ logger->inc(l_bluestore_reads_with_retries);
++ dout(5) << __func__ << " read at 0x" << std::hex << offset << "~" << length
++ << " failed " << std::dec << retry_count << " times before succeeding" << dendl;
++ }
+ return r;
+ }
+
+@@ -6993,6 +7015,13 @@ int BlueStore::_verify_csum(OnodeRef& o,
+ uint64_t bad_csum;
+ utime_t start = ceph_clock_now();
+ int r = blob->verify_csum(blob_xoffset, bl, &bad, &bad_csum);
++ if (cct->_conf->bluestore_debug_inject_csum_err_probability > 0 &&
++ (rand() % 10000) < cct->_conf->bluestore_debug_inject_csum_err_probability * 10000.0) {
++ derr << __func__ << " injecting bluestore checksum verifcation error" << dendl;
++ bad = blob_xoffset;
++ r = -1;
++ bad_csum = 0xDEADBEEF;
++ }
+ if (r < 0) {
+ if (r == -1) {
+ PExtentVector pex;
+diff --git a/src/os/bluestore/BlueStore.h b/src/os/bluestore/BlueStore.h
+index 6a14042df..70050a567 100644
+--- a/src/os/bluestore/BlueStore.h
++++ b/src/os/bluestore/BlueStore.h
+@@ -118,6 +118,7 @@ enum {
+ l_bluestore_extent_compress,
+ l_bluestore_gc_merged,
+ l_bluestore_read_eio,
++ l_bluestore_reads_with_retries,
+ l_bluestore_last
+ };
+
+@@ -2366,7 +2367,8 @@ public:
+ uint64_t offset,
+ size_t len,
+ bufferlist& bl,
+- uint32_t op_flags = 0);
++ uint32_t op_flags = 0,
++ uint64_t retry_count = 0);
+
+ private:
+ int _fiemap(CollectionHandle &c_, const ghobject_t& oid,
+diff --git a/src/test/objectstore/store_test.cc b/src/test/objectstore/store_test.cc
+index d2152d456..326c9785d 100644
+--- a/src/test/objectstore/store_test.cc
++++ b/src/test/objectstore/store_test.cc
+@@ -6855,6 +6855,73 @@ TEST_P(StoreTestSpecificAUSize, fsckOnUnalignedDevice2) {
+ g_conf->apply_changes(NULL);
+ }
+
++TEST_P(StoreTest, SpuriousReadErrorTest) {
++ if (string(GetParam()) != "bluestore")
++ return;
++
++ ObjectStore::Sequencer osr("test");
++ int r;
++ auto logger = store->get_perf_counters();
++ coll_t cid;
++ ghobject_t hoid(hobject_t(sobject_t("foo", CEPH_NOSNAP)));
++ {
++ ObjectStore::Transaction t;
++ t.create_collection(cid, 0);
++ cerr << "Creating collection " << cid << std::endl;
++ r = store->queue_transaction(&osr, std::move(t), nullptr);
++ ASSERT_EQ(r, 0);
++ }
++ bufferlist test_data;
++ bufferptr ap(0x2000);
++ memset(ap.c_str(), 'a', 0x2000);
++ test_data.append(ap);
++ {
++ ObjectStore::Transaction t;
++ t.write(cid, hoid, 0, 0x2000, test_data);
++ r = store->queue_transaction(&osr, std::move(t), nullptr);
++ ASSERT_EQ(r, 0);
++ // force cache clear
++ EXPECT_EQ(store->umount(), 0);
++ EXPECT_EQ(store->mount(), 0);
++ }
++
++ cerr << "Injecting CRC error with no retry, expecting EIO" << std::endl;
++ g_conf->set_val("bluestore_retry_disk_reads", "0");
++ g_conf->set_val("bluestore_debug_inject_csum_err_probability", "1");
++ g_ceph_context->_conf->apply_changes(nullptr);
++ {
++ bufferlist in;
++ r = store->read(cid, hoid, 0, 0x2000, in, CEPH_OSD_OP_FLAG_FADVISE_NOCACHE);
++ ASSERT_EQ(-EIO, r);
++ ASSERT_EQ(logger->get(l_bluestore_read_eio), 1u);
++ ASSERT_EQ(logger->get(l_bluestore_reads_with_retries), 0u);
++ }
++
++ cerr << "Injecting CRC error with retries, expecting success after several retries" << std::endl;
++ g_conf->set_val("bluestore_retry_disk_reads", "255");
++ g_conf->set_val("bluestore_debug_inject_csum_err_probability", "0.8");
++ /**
++ * Probabilistic test: 25 reads, each has a 80% chance of failing with 255 retries
++ * Probability of at least one retried read: 1 - (0.2 ** 25) = 100% - 3e-18
++ * Probability of a random test failure: 1 - ((1 - (0.8 ** 255)) ** 25) ~= 5e-24
++ */
++ g_ceph_context->_conf->apply_changes(nullptr);
++ {
++ for (int i = 0; i < 25; ++i) {
++ bufferlist in;
++ r = store->read(cid, hoid, 0, 0x2000, in, CEPH_OSD_OP_FLAG_FADVISE_NOCACHE);
++ ASSERT_EQ(0x2000, r);
++ ASSERT_TRUE(bl_eq(test_data, in));
++ }
++ ASSERT_GE(logger->get(l_bluestore_reads_with_retries), 1u);
++ }
++
++ // revert
++ g_conf->set_val("bluestore_retry_disk_reads", "3");
++ g_conf->set_val("bluestore_debug_inject_csum_err_probability", "0");
++ g_ceph_context->_conf->apply_changes(nullptr);
++}
++
+ int main(int argc, char **argv) {
+ vector<const char*> args;
+ argv_to_vec(argc, (const char **)argv, args);
+--
+2.19.2
+
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